The present invention relates to the manufacture of integrated circuits. More particularly, the invention provides a technique including a method and an apparatus for chemical mechanical polishing using a device that maintains substantially parallel alignment between a surface of a film being polished and a rotating polishing surface, as well as other features. Among other benefits, parallel alignment tends to produce more uniformity in the film being processed and maintains film quality.
Chemical mechanical polishing or planarization (xe2x80x9cCMPxe2x80x9d) is a technique of polishing materials including semiconductor substrates and films overlying such substrates, which provides a high degree of uniformity and planarity. The process is used to remove high elevation features on films created during the fabrication of a microelectronic circuitry on the substrate, or to remove a layer of film to reveal the circuitry buried underneath the film. In some cases, the process can even planarize semiconductor slices prior to the fabrication of microelectronic circuitry thereon.
A conventional chemical mechanical polishing process uses an apparatus having a single large polishing pad positioned on a platen, against which a substrate is positioned for polishing. A positioning member positions and biases the substrate to be polished against the polishing pad, which is rotating. A chemical slurry, which is likely to have abrasive materials, is maintained on the polishing pad to modify the polishing characteristics of the polishing pad and to enhance the polishing of the substrate or films.
Unfortunately, chemical mechanical polishing is not free from limitations in the manufacture of integrated circuits. For instance, CMP is extremely time consuming, which generally influences wafer throughput. Additionally, the polishing pad often accumulates residual by-products from the polishing operation or wears and deforms the polishing pad, which leads to degradation of the polishing efficiency for the polishing operation. Furthermore, the apparatus with the single polishing pad can only perform a single process such as dielectric layer polishing or tungsten film polishing, thereby requiring an additional apparatus to perform other processes. Moreover, conventional CMP of large substrate surfaces tends to be problematic, since it is often difficult to maintain parallel alignment between a substrate surface and a rotating polishing surface using conventional techniques. Accordingly, conventional chemical mechanical polishing has a variety of limitations.
From the above, it is seen that a technique for chemical mechanical polishing which is cost effective and efficient is often desirable.
According to the present invention, an improved technique for chemical mechanical polishing is provided. In particular, the technique uses an apparatus having a multi-head turret for providing chemical mechanical polishing using one of a plurality of polishing surfaces. In an exemplary embodiment, each of the carrier devices, which secures a workpiece to be processed, is coupled to a common turret by way of at least two fingers that are pivotable to secure each carrier device in parallel alignment to one of a plurality of the polishing surfaces. These two fingers that are pivotable absorb process non-uniformities to maintain parallel alignment between a surface of the workpiece and the polishing surfaces.
In a specific embodiment, the present invention provides an apparatus for chemical mechanical polishing using a plurality of carrier devices rotatably coupled to a turret means. The apparatus includes the turret means and a plurality of rotatable polishing surfaces (e.g., rotating polishing pad and platen) positioned around the turret means. The apparatus also includes a plurality of carrier devices and rotatably coupled to the turret, where the carrier devices are each adapted to hold a workpiece (e.g., a wafer, a semiconductor wafer, a patterned semiconductor wafer, a plate, hard drives, a display panel, a substrate, and magneto resistive read-write heads) to be polished on at least one of the rotatable polishing surfaces. Each of the carrier devices is operably independent to each other during a process for chemical mechanical polishing. Accordingly, each of the carrier devices can move freely in three dimensions, e.g., vertical, radial, and angular, i.e., rotational or tangential. In preferred embodiments, each of the carrier devices, which secures a workpiece, is coupled to a common turret by way of at least two fingers that secure each carrier device in parallel alignment to one of a plurality of the polishing surfaces. Parallel alignment is maintained over any substantial variations in processing conditions.
In an alternative embodiment, the present invention provides a method of processing a surface of a workpiece using, for example, an apparatus for chemical mechanical polishing. The method includes steps such as securing a workpiece onto a carrier device, where the film to be processed faces away from the carrier device. The method positions a surface of the workpiece against a rotatable polishing surface, which biases the face against the rotatable polishing surface. In a specific embodiment, the workpiece is rotating and the rotatable polishing surface is also rotating as the face is biased. The method also includes a step of maintaining a substantially planar or parallel configuration between the surface of the workpiece and the rotatable polishing surface. Such maintaining step occurs by at least two fingers or pivotable members operable coupled to the spindle of the carrier device. In operation, the two fingers are in a substantial parallel alignment position relative to each other, which keeps the spindle in a substantial normal position relative to the surface of the workpiece. Variations in a process that cause the spindle to move out of a normal position can be absorbed by the two fingers or pivotable members, which couple to the fingers by movable couplings. Parallel alignment is maintained over any substantial variations in processing conditions.
Benefits are achieved using the present invention. In particular, the multi-carrier design allows for higher wafer throughput over pre-existing techniques. Additionally, a variety of polishing processes (or recipes) can be performed using the present apparatus. Furthermore, each of the carriers can be adjusted in two or three dimensions independent of each other to achieve desired processing conditions. Additionally, the use of more than one finger coupled to a carrier device maintains a surface of a workpiece secured by the carrier device in substantially parallel alignment to a rotating polishing surface, which provides for a more uniform and accurate polishing process. These and other benefits are described throughout the present specification, and more particularly below.
The present invention achieves these benefits in the context of known process technology. However, a further understanding of the nature and advantages of the present invention may be realized by reference to the latter portions of the specification and attached drawings.